Soil acidification alters C : N : P stoichiometry in the soil due to higher acid sensitivity of phosphorus

Soil acidification seriously affects the structure and functions of terrestrial ecosystems, but the impact of soil acidification on the stoichiometry of soil C : N : P remains inconclusive. Therefore, a greenhouse experiment was conducted to investigate the response of soil C, N and P stoichiometry to soil acidification in a simulated agricultural planting system, with five soils (including acid sulfate soil, red soil, lateritic red soil, latosol and limestone soil) that had different initial properties being used. Four soil acidification levels were created by adding acid solutions with pH of 5.0, 4.0, 3.0 or 2.0, along with a control with the pH of 7.0. The results showed that the experimental treatments resulted in significant soil acidification (p < 0.05), with the pH 2.0 treatment inducing a decline in soil pH ranging from 12.43% to 32.22% in the five soils. However, soil acidification did not significantly change soil organic C content, except in the cases of the strong acidification treatment in lateritic red soil and limestone soil, whereas it significantly or marginally significantly increased soil total N content in the five soils. Across the five soils or in each soil, the acidification treatments consistently and significantly linearly reduced soil total P content, with the pH 2.0 treatment resulting in soil total P reduction by 32.90%, 21.78%, 27.82%, 25.93% and 30.67% in acid sulfate soil, red soil, lateritic red soil, latosol and limestone soil, respectively. Correspondingly, soil available P content significantly increased under acidification treatments. Such asymmetrical responses of soil C, N and P contents resulted in significant alterations in soil C : N : P stoichiometry under acidification scenarios, with soil C : P and N : P ratios increased significantly. These results suggest that soil acidification may increase soil C : P and N : P ratios mainly by decreasing soil total P content, due to the activation of soil P as available P components.